Process for the production of rails



Jly 27, 1937.

v VFn'ocss Fon Tar: PRODUCTION oF uns Fnedlarch 31, 1934 Vif Royer? Eff H. J. VAN RoYEN 2,088,282

` Patented July 27, 1937 PROCESS FOR THE PRODUCTION OF'RAILS Herman Johan van Royen, Hoorde, Germany `Application March 31,

V1934. Serial No. 718,493

In Germany April 10, 1933 i 7 Claims.

This inventionhrelates to an improvement in the manufacture of rails from a steel of eutectoid composition and of lamellar pearlitic structure as Well as to the improved rails thus obtained.

Carbon steels containing about 0.9% of `carbon and thus possessing the so-called eutectoid composition have the lamellar-pearlitic structure if they are protected from too rapid cooling after rolling. If said steels have an increased content of manganese (more than 0.5%) or if they contain further so-called double carbide forming elements especially 'molybdenunn the steel must have `a carbon content lower than 0.9% morder to maintain the eutectoid composition. For instance an unalloyed steel with 0.75% of manga.-

nese has the eutectoid `composltionwith a carbon' content of. 0.75% and a. molybdenum steel with 0.3% of molybdenum and 0.65% of manganese with `a. carbon content of 0.80%.

The present invention relates to a process for the treatment of steels with eutectoid composition and lamellar-pearlitic structure in which the as steels of lower hardness.

carbon content lies below 0.9%, more particularly and containing manganese l preferably between about 0.6 and and molybdenum up to 0.3%. In addition thereto small amounts of the further double carbide forming elements chromium, tungsten,`

vanadium may be present singly or together. In this case the manganese content may be decreased to about 0.5%.

The present invention aims at providing a process, the purpose of which is to impart to wear-resisting steels of the aforesaid composition and structure a further improvement of those mechanical properties, especially with regard to shock and impact stresses, which are important in practical use. According to the experience of the German State Railways, considerable importance must be attached in the case of steels with high resistance to wear and increasedhardness tothe requirement that said steels should behave just as well under the` conditions of impact tests, In addition the reliable prevention of `fractures under continuous l stressing is a matter of the highest importance.

` These phenomena of iracture are attributable to the formation of hair cracks in the rail head and, consequently, if the formation of suchcracks can be reliably prevented',` the prevention of fractures under continuous granted.

It has been ascertained in accordance with the present invention that an important improvement can be obtained, in relation to the aforesaid two 5 requirements, by the maintenance of definite temperature conditions'in rollingithesteel so that when the temperature has fallen to about 1000 C. in the penultimate pass, the rolling is not continued immediately, the material beingfon the 10 contrary, allowed to cool until its temperature `has fallen to a little above 900'" C. and then con tinuingrolling in the nal pass at-that tempera ture, in which event the end temperature will be slightly below 900 C.

This method of working is suitably performed by starting with comparatively small ingots which are first allowed to cool gradually and then slowly re-heated before rolling. The ingots should weigh about 2 to 2.5 tons; The slow cooling can 20 be eiected by allowing the ingots to remain longer than usual in the moulds, and consequently for about 5 hours, instead of the us'ual periodof two hours.

Astressing may be taken for According to the present invention, therefore, 25

preferably be continued until room temperature 30,

is reached. After the second pass the temperature is about l180 C. and after the klast pass but One, about 1000-1050 C. After the penultimate pass the material is allowed to cool` down to 910- 900"` C. and is then put through the iinal pass, 354

so that its temperature descends through the 900 C. level during that operation. It has also been found` advisable to make arrangements so that the rail, which in the ordinary method of treatment bends considerably on the cooling bed, 40 and has to be subjected to extensive deformation in cold straightening, is already substantially straightened on the cooling bed. For this purpose the rail, after leaving the rolls, and therefore `in a warm state, is subjected to a preliminary bending oi' such a character as to be counter, in direction and extent, to'that experienced by the rail in cooling. Under this treatment, the steel leaves the coollngbed in a nearly straight condition so that its shape requires to be only ...anun

slightly modified afterwards. This treatment also contributes to furnishing a product of maximum reliability.

This feature of the present invention is illustrated by way of example with reference to the accompanying drawing in which Fig. 1 is a side view showing the curved condition of a rail after normal treatment.

Fig. lL is a transverse section of the rail.

Fig. 2 illustrates in which manner the rail is preliminarily bent according to the invention.

Fig. 2a is a transverse section of the rail shown in Fig. 2.

Figs. 3 and 4 are side views of rails subjected to impact tests.

In order to obtain the finished rail in nearly straight condition the rail is subjected to a preliminary bending contrary to the deformation otherwise occurring in the rails.

In order not to disturb the development of the lamellar-pearlitic structure of the steel while cooling the steel must be protected against excessive loss of heat, in known manner. With this object the steel is not cooled on the cooling bed in the usual manner, but is inserted at about 750 C. under an insulated hood, and left to cool therein to about 500 C. whereupon it can be further cooled in the air.

According to the facts I have ascertained, the prevention of the cracks is not attributable to the retarded cooling which, on thev contrary, serves merely to ensure the development of the lamellar-pearlitic structure. The dangerous ,transverse cracks do not appear even when the specified measures for retarding the cooling are omitted.

The following is a preferred composition of the steel: Carbon W13-0.80%, manganese 0.800.65%, molybdenum 0.3-0.2%. 0.15% may be taken as the minimum content of molybdenum from which an effect in the sense of the invention can be expected. The molybdenum may be entirely or partially replaced by chromium, tungsten or vanadium, in which event the manganese content can be reduced to about 0.5%. In any case, however, care must be taken to preserve the eutectoid structure. Therefore the following upper limits are to be observed:

Percen Chromium up to about 0.5 Tungsten up to about 0.7 Vanadium up to about 0.2

For instance favourable results were obtained with steels of the following composition 0 Mn Mo Cr W V Percent Percent Percent Percent Percent Percent 0. 12 0. 05 0. 21 0. 4o 0.68 0.68 0.30 0.47 Balance substan- 0. 0.58 0.20 0. so 0.35 0.20 tiailyiron. o. 7s o. 75 0. 15 0. 10

.The secondary components, such as silicon, phosphorus and sulphur are present to the same First blow 5000mkg., each additional, 3000 mkg. Weight of hammer 1000 kg., prescribed bend mm.

Mean deflec- Method of manulac- Type o( wear-resisting tion prior ture of the rails steel to fracture Ordinary ;r Euteetoid carbon steel 84 with 0.75-0.80% of C. and M50-0.70% Mn. Eutectoid steel with 0.70- 87 0.75% of C., 01m-0.50% ot Mu and 0.4-0.5% of Eutectoid steel with 0.73-

0.30% of C., QSO-0.65% of Mn and Oli-0.2% oi Mo.

Normal Mo steel with eutectoid structure.

Steel oi same composition, treated in accordance with the process oi the present invention.

The manner in which the invention may be carried into practice is more particularly illustrated by the following examples:

From melts of the following composition:

Melt C Mn P Si S Cr Cu Mo C 0. 75 0. 74 0. 034 0. 28 0. 018 0. Oli 0. 25

Alter the Alter the pc- Melt second pass nultimnie pass 1170 U90 11S() lill() 1180 i020 1190 1010 'I'hereupon the rails were left to cool down to about 900 C. and passed the nal calibre at this temperature.

From each rolling length two rails of 15 meters were cut. On the cooling bed said rails were bent through over the foot. By a preliminary bending of about 500 mm. it could be obtained that they were almost straight when the cooling was complete. After the preliminary bending the rails passed an isolated hood. The travelling time amounted to about 'half an hour. When leaving the hood they were found to have a temperature between about 500 and 520 C.

Results of impact tests The impact tests were carried out after the` prescriptions ,of the German State Railways.

`First blow 5000 mkg.; each additional, 3000 mkg.

Weight of hammer 1000 kg., prescribed bend 80 M enn deflection mm.

The `improved rail obtained in accordance with my invention is distinguished from rails of lthe r same composition which have been rolled in ordinary manner by being free from cracks and possessing a substantially higher deflection, as

` illustrated bythe foregoing examples. The mean `deflection obtained under impact stresses is furthermore illustrated by reference to the accompanying drawing in which y Fig. 3 shows a railthe head of which has been subjected to the impact test prescribed by the German State Railways, the conditions of which are above referred to.` 'Ihetest was` interrupted after 'blows, the deflection amounted to 156 mm. i

Fig. 4 shows arail the foot of which has been subjected to an impact test under the same conditions above referred to. The foot received 8 blows and had a deflection of 110 mm. i

It may be remarked that the method above described maybe altered in variousrespects without departing from the spirit of my invention. lThus it is,` of course, possible to obtain the lamellarpearlitic structure in the rolled articles by cooling them in a covered or non-covered excavation or pit or by retarding the cooling in any other i manner. Such details in the performation of my .invention are, of course, quite familiar to those` skilled in the art.

`What -I claim and desire to secure by Letters Patent of the United States is:l

1. A process for the production of rails by rolling from a steel containing between about 0.65

and 0.80% of carbon, between abut 0.5 and 0.8%

of `manganese and between about 0.15 and 0.3%

"of molybdenum, which comprises cooling the work to a temperature somewhat above 900 C. prior to the nnal pass so that it vleaves the final pass with a temperature below about 900 C.

2.` A process for the production of rails by rolling from a steel containing between about 0.65

and 0.80% of carbon,`between about 0.5 and 0.8% of manganese and between about 0,15 and 0.3% of molybdenum in `which small ingots` of a weight of about 2 to 2.5 tons of said steel are subjected to a. rolling treatment in which the work is cooled to a temperature somewhat above 900 C. prior `to the final pass so that it leaves the nal pass with a temperature below 900 C.

3. A process for the production of rails by., rrolling from a steel containing between about 0.65 and 0.80%.of carbon, between about 0.5 and 0.8% of manganese and between about 0.15 and 0.3% of molybdenum which comprises castlng small ingots of a weight of about 2 to 2.5

tons from said steel, cooling said ingots to ordinary temperature, reheating them to the temperature required for rolling and finally rolling them into rails of the desired shape, cooling the work to aj temperaturesomewhat above 900 C. dur- 1 `ing the rolling prior to the final pass so that it leaves the final pass with a temperature below about 900 C.

4. A process for thel production of rails by` rolling from a steel containingbetween about 0.65 and 0.80% of carbon, between about 0.5 `and 0.8% of manganese andbetween about 0.15 and 0.3% of molybdenum which comprises casting small ingots of a weight of about 2 to 2.5 tons from said steel, cooling said ingots to ordinary temperature, reheating them to the temperature required for rolling and nally rolling them into rails of the desired shape, cooling the work to a'temperature somewhatv above 900 C.,

during the rolling prior tothe nal pass, so that it leaves the nal pass with a temperature below about 900c C., thereafter subjecting the rail `to a .preliminary bending, counteracting the bending stresses occurring after cooling and finally retarding cooling of the rail on the cooling bed so that the development of the lamellar-pearlitic structure is preserved.

5. A process for the production of rails by rolling from a steel containing between about 0.73 and 0.80% of carbon, between about 0.80 and 0.65% of manganese and between about 0.3 and 0.2% of molybdenum in which small ingots of a weight of about 2 to 2.5 tons of said steel are subjected toa rolling treatment in which the work is cooled to a temperature somewhat above 900 C. prior to the final pass sothat it leaves the final pass with a temperature below 900 C.

6. A process for the production of rails by rolling from a steel containing between about 0.73 and `0.80% of carbon, between about 0.80 and 0.65% of manganese and between about 0.3 and 0.2% of molybdenum which comprises` casting small ingots of a weight of about 2to`2.5 tons from said steel, cooling sai-d ingots to ordinary temperature, reheating them to the temperature required for rolling and finally rolling them into rails of the desired shape, coolingthe work to a temperature somewhat above 900 C. during the rolling prior to the nal pass so that it leaves the nnalpass with a temperature below about 900 C.

7. A process for the production of rails by rolling from a steel containing between about 0.73 and 0.80% of carbon, between about 0.80 and 0.65% of manganese, and between about 0.3 and 0.2% of molybdenum which comprises casting `required for rolling and nnally rolling them into rails `of thedesired shape, cooling the Work to a temperature somewhat above 900 C. during the rolling prior toythe inal pass, so that it leaves the nal pass with a temperature below about 900 C., thereafter subjecting the rail to a preliminary bending counteracting the bending stresses occurring aftericooling and lnally retarding the cooling of the rail on the cooling bed so that the development of the lamellar-pearlitic structure ls preserved.

HERMAN JOHAN VAN ROYEN. 

